Free flooded deep submergence transducer

ABSTRACT

A right cylinder of piezoelectric ceramic is centered in a hollow annulus. The annulus is filled with high dielectric oil so that hydrostatic pressure regardless of magnitude is perfectly equalized inside and outside the annulus to obviate all pressure gradiants. The annulus comprises two coaxial rubberlike tubes, transparent to acoustic energy, and attached with simple hose clamps to metal rings at the ends of the cylinder.

United States Patent 340/10 340/l0 340/l l ml d ea w n mmmma e.mP. n mm m M o o .r HJMK Dm 5668 w 6666 r 9999 H HHHH i. 4773 mm mm 399 8908 1 WM 8235 at 7667 Mb nm 3333014 a k u m A t m m n w n" mm w BC Dim ,t wmnsmm 5 UVE 0 4u h J -JNT r Q e o N we m M 8 mwe V ots n tl as l AFPA 2 UN 7 2247 represented by the Secretary of the Navy Attorneys-J. C. Warfield, George .I. Rubens, John W.

McLaren and Truman L. Styner I 54 I FREE F LOODED DEEP SUBMERGENCE piezoelectric ceramic is cen- TRANSDUCER ABSTRACT: A right cylinder of tered in a hollow annulus. The annulus is filled with high pressure regardless of mage and outside the annulus to The annulus comprises two 1 Claim, 5 Drawing Figs.

310/91, dielectric oil so that hydrostatic 310/89, 340/10 nitude is perfectly equalized insid Int. ob iate all pressure gradiants- 310/89, coaxial rubberlike tubes, transparent to acoustic energy, and 9.6; 340/10 attached with simple hose clamps to metal rings at the ends of the cylinder.

[56] References Cited UNITED STATES PATENTS 12/1962 Andrews,Jr..................

BIO/9.1 X

PATENTEDNUV 30 Ian SHEET 10F 2 T 5 ma n N N N R R m V w w r A FREE FLOODED DEEP SUBMERGENCE TRANSDUCER The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

BACKGROUND Any pressure release mechanism to dissipate the back lobe energy of a transducer, invariably results in a hydrostatic pressure differential between the front and rear radiating surfaces of the transducer. Hence, as the depth of submergence increases, a pressure is soon reached which immobilizes the vibratory element ofthe transducer.

Accordingly, an object of this invention is to provide an improved transducer for operation at any depth of submergence.

SUMMARY The object of this invention is attained by an open-ended right cylinder of piezoelectric material enclosed in a hollow annulus. The materials of the annulus are transparent to the acoustic energy to be transmitted from or received by the element. The annulus is filled with transformer oil or other fluid of good dielectric properties. Since any hydrostatic pressure is applied equally to all surfaces of the annulus and hence, through the oil to the piezoelectric element, there can be no pressure gradients in this system nor immobilization of the element. A simple unique structure is employed for making liquidtight seals between parts of the annulus.

Other objects and features of this invention will become apparent to those skilled in the art by referring to the specific embodiment described in the specification and shown in the accompanying drawing in which:

FIG. 1 is a perspective view of the transducer according to this invention ready for use,

FIG. 2 is a sectional view of the transducer of this invention, the section being taken on line 2-2 of FIG. 1,

FIG. 3 is an enlarged detail view in perspective and partly in section to show one of the ceramic holding mechanisms employed in this invention,

FIG. 4 is a detail of an oil filler cap taken on line 4-4 of FIG, I, and

FIG. 5 is a detail of a support lug taken on line 55 of FIG. I.

The active element of the transducer of this invention is preferably a ceramic, such as barium titanate, which has been electrically polarized and baked to give the ceramic optimum piezoelectric properties. The active element is in the form of a right cylinder and is shown at in the drawings. The desired mode of operation of the ceramic is circumferential and to that end the ceramic cylinder is fabricated of a large number of staves. The abutting edges of the staves are covered with a film or foil of good conducting metal such as silver and are joined as by soldering. Alternate films are connected together and to external lead-in conductors to which are connected the transmitting and/or receiving gear. The lead-in bushings are shown at I2 and 14, FIG. I. The inner end ofeach lead-in conductor is connected to a bus bar which is disposed near one end of the transducing element.

The cylindrical ceramic element is coaxial with and is completely enclosed by the hollow annulus 16. The annulus is substantially rectangular in cross section and the ceramic element is centered, approximately, in the rectangular annular space. After assembly, the entire annular space is filled with a transformer oil or other liquid having good dielectric properties to suitably insulate the terminals 12 and 14 and bus bars upon which are applied signals of fairly high voltages. The annulus comprises inner and outer tubes 18 and 20 of rubber or rubberlike material or a semisoft plastic which has sufficient strength to support the structure but which is transparent to the acoustic energy that must be radiated to or from the ceramic element. The diameters of the tubes 18 and 20 are different so that one may be telescoped inside and the other outside the ceramic element. To complete the casing for the transducer, the rings 22 and 24 are sealed liquid tight at the ends of the tubes I8 and 20. The rings 22 and 24 are each channel shaped in cross section, and the flanges of the channels are so adjusted in ring diameter as to slip snugly into the interior of the tubes 18 and 20, respectively. Both clamps 22a and 24a at opposite ends of tube 18, clamps tube 18 to the outer flanges of the metal rings. Likewise, clamps 22b and 24b clamp opposite ends of tube 20 to the inner flanges of the two rings. Any conventional hose clamp tensioning device 240 may be employed to tighten the straps on the tubes. Uniquely, the tubes are slipped over the outside of each flange of each ring 22 and 24 so that tension only in the "clamps is employed.

For a piezoelectric ceramic to operate properly it must freely expand and contract in response to the signal voltage applied. For this reason, the ceramic cylinder 10 must float" freely within the annular space of the container. In FIG. 3, there is shown details of one effective clamp for centering the ceramic in the housing without restricting motion of the element. Four clamp assemblies of the type shown in FIG. 3 are found to be adequate for supporting a ceramic element which is no more than 15 or 20 inches in diameter. Each clamp assembly comprises blocks 30 attached as by screws and/or silver soldering to the outside flanges of rings 22 and 24, respectively. The upper and lower edges of the ceramic cylinder ride in insulating blocks 33 of material such as teflon. The teflon blocks in turn straddle rubber blocks 32 which are sufficiently resilient to insulate the ceramic from external shock. Blocks 32 straddle metal clips 31 which are screwed to blocks 30. One end of strap 34 of electrical insulating properties is caught under the clips 300 at the top of the cylinder, is passed under clip 31 at the bottom, and hence under clip 31 at the top. The strap is tightened to hold the assembly together without restraint upon motion of the ceramic cylinder. A webbing or tape of fiber glass, is a good insulator, and is strong yet yieldable to vibrations in the ceramic.

In assembly, the tube 20 is clamped in place by clamps 22b and 24b and at the same time the ceramic element I0 is anchored in the FIG. 3 blocks, and the tapes 34 tightened. At this juncture, the clamps 24c are easily tightened with a screwdriver having a long shank. Next, the outer tube 18 telescoped over the assembly and the straps 22a and 24a are tightened. Finally, the caps 36, see FIG. 4, are removed and the entire annular container is filled with transformer oil or other high dielectric liquid. Two or more openings are preferably provided so as to eliminate the possibility of air bubbles in the oil. Without occluded air, most oils are substantially incompressible. Even at a depth of submergence of, say, 10,000 feet, the amount of distortion of the container of FIG. I is negligible.

To handle and mount the now relatively heavy transducer, lugs 37 are conveniently provided at several points on the upper ring to which may be attached lifting brackets. Since it is now apparent that the pressure within the annular container is substantially the same as the pressure outside there can be no differential pressure and hence no strain upon the seals. The transducer of FIG. 1 can be subjected to any hydrostatic pressure without impairing the efficiency of operation of the transducer.

What is claimed is:

1. A deep submergence transducer assembly comprising a cylindrical piezoelectric element,

an annular chamber enclosing said cylindrical element, said chamber being filled with insulating liquid, the walls of the chamber comprising two coaxial tubes of different diameters and disposed, respectively, inside and outside said cylindrical element,

rings at opposite ends of said element, said rings each being channel shaped in cross section with a lateral portion and substantially coextensive coaxial flanges, said flanges being telescoped, respectively, into and sealed to the ends of said tubes for retaining said insulating liquid within the chamber, while permitting flooding and direct coupling of acoustic energy from the interior wall of said annular 3 4 chamber. as well as the exterior wall thereof. to the suryieldable insulating blocks between each metal block and founding y of water the edge of said piezoelectric element and lead'in sealed through one of said rings a tautened strap of insulating material encircling the blocks nected to sand element of each pair of said element to yieldably join the parts of means for supporting said cylindrical piezoelectric element 5 concentrically in said annular chamber including a plurality of pairs of metal blocks. the blocks of each pair being affixed. respectively. to said rings.

the transducer in a unitary assembly without restricting the motion of said element.

t 1 t l 0 

1. A deep submergence transducer assembly comprising a cylindrical piezoelectric element, an annular chamber enclosing said cylindrical element, said chamber being filled with insulating liquid, the walls of the chamber comprising two coaxial tubes of different diameters and disposed, respectively, inside and outside said cylindrical element, rings at opposite ends of said element, said rings each being channel shaped in cross section with a lateral portion and substantially coextensive coaxial flanges, said flanges being telescoped, respectively, into and sealed to the ends of said tubes for retaining said insulating liquid within the chamber, while permitting flooding and direct coupling of acoustic energy from the interior wall of said annular chamber, as well as the exterior wall thereof, to the surrounding body of water, lead-in conductors sealed through one of said rings connected to said element, means for supporting said cylindrical piezoelectric element concentrically in said annular chamber including a plurality of pairs of metal blocks, the blocks of each pair being affixed, respectively, to said rings, yieldable insulating blocks between each metal block and the edge of said piezoelectric element, and a tautened strap of insulating material encircling the blocks of each pair of said element to yieldably join the parts of the transducer in a unitary assembly without restricting the motion of said element. 